Poor services : Sleepmaster N1 City

I bought a Sealy Olympia bed in October 2021. After 3 months the mattress has started sagging on the one side. When I phoned to complain about it, I was told that I had to come into the shop to complete a claim form. I did that on Thursday 06/01 and is still waiting on them. Phoned the shop and Customer services also. No service yet. Will not recommend this shop.